The present invention relates to a simplified catadioptric erect image telescope system of the Gregorian type where the primary or main mirror is flat surfaced with a central aperture and is positioned at the intersection of two axes of the system and where the collecting mirror is concave. In particular, the present invention relates to a preferred system where the main mirror is about one-half or less than the diameter of a plural element refractor which introduces light into the system on a first axis corrected for aberrations and focuses it towards the flat main mirror which is inclined to the first axis and which reflects the light on a second axis towards the concave secondary mirror in an inverted image after first focusing and then the concave mirror produces an erect image, elongated focus behind the aperture which can be viewed behind the aperture on the second axis with an eyepiece.